1. Field of the Invention
The present invention relates to an apparatus for chipping materials having an adjustable cutting angle.
2. Description of the Background Art
Devices of this class are known from a wide variety of models. DE 101 25 922 A1, for example, has a knife ring chipper for timber. Its chipping unit has a chipping chamber around which a ring of knives are arranged. The chipping unit includes two ring wheels, which are concentrically arranged around an axis of rotation, the ring wheels being connected to axis-parallel knife carriers, which are distributed around a perimeter of the ring wheels in a circular fashion. With their base facing the axis of rotation, the knife carriers form the boundary of the chipping chamber. Due to the spacing between the knife carriers, axis-parallel slots are formed. Each knife carrier has a bearing surface that is angled towards its base for an accurate incorporation of the slicing knife. In this position, the slicing knife extends through the axial slot with a predetermined blade length projecting into the chipping chamber, and with the backside of the preceding knife carrier forms a comminution channel for the passage of the chipped material. The angle of inclination between the slicing knife and the base of the knife carrier is equal to the cutting angle, which typically is in the range of approximately 30° to 45° and is immutably determined by the geometry of the knife carrier.
A similar device is known from DE 198 48 233 A1, which also discloses a knife ring chipper, and in which small-particle material is fed in an airflow to the knife ring. For the comminution of the material, a striker wheel acts jointly with the knife ring, both of which rotate in opposite directions and thus move the small-particle material past the blades of the slicing knives. Apart from counter-rotating chipping tools, simpler models are also known, whereby the knife ring is stationary and only the striker wheel rotates, or whereby only the knife ring rotates and the blades are moved past a stationary counter-knife. All of these devices have in common that the structure of the knife ring is basically as previously described, in particular, that the knife carriers have a rigid bearing surface for the slicing knives that determines the cutting angle.
Conventional cutting disks have a comminution unit that includes a rotating disk with an opening that is arranged in a semi-radial direction along which the knife carriers with slicing knives are arranged. The knife carriers, in turn, have a bearing surface that is inclined towards the disk plane for attaching the slicing knife, whose inclination determines the cutting angle. Such a cutting disk is known from DE 100 48 886 C1, for example, wherein a cutting disk is used in a first stage of comminution. The special feature of this device is the combination with a second stage of comminution, which is formed from a ring of knives as previously described.
All of the conventional art previously described have in common that the position of the slicing knife in relation to the chipping chamber, and therefore the cutting angle, are immutably determined by the fixed geometry of the knife carrier. In many areas of application, this constant cutting angle may be sufficient. However, increased demands regarding the quality of the chips and the economical operation of comminution devices make it imperative to continue to improve devices of this class.